1. Field of the Invention
The invention relates to fiber-reinforced, pourable, vegetation soil substrates. Such are useful as vegetation supports for surfaces such as roofs and the like.
2. Description of the Prior Art
Vegetation soil substrates are known in the art, as exemplified by GB-A-2 274 997. Such substrates are particular useful for sports grounds having grass surfaces and which are greatly stressed by sportsmen. The organic substrate constituents in this prior disclosure are exclusively formed by peat and top soil. For stabilizing roots, synthetic single plastic fibers in quantities of 0.9 to 0.4 wt. % are proposed. FR-A-2 442 809 relates to a fiber substrate for improving plant growth and which can comprise natural and synthetic substances. The substrate can be in mixed form and can be produced both from new and recycled materials having a fiber length of 1 to 2 cm, such as cardboard, hardboard and textiles.
Numerous different types of pourable vegetation soil substrates exist and can be adapted to the particular desired greening use. In certain layer thicknesses of 0.5 to 30 cm they form an artificial soil structure, namely a vegetation support layer, for absorbing or receiving the actual vegetation and optionally precipitation and irrigation water. Vegetation soil substrates are also known in the art from DE-B-24 59 269 and DE-C-832 897.
The art also discloses vegetation mats, e.g. from EP-B-608 450 and the references cited therein, which offers a survey of further prior publications and literature. Each of these disclosures is incorporated herein by references.
During periods of drought, ground water is consumed both by plants via their roots for growth purposes, and also by evaporation, as via the leaves. Independent of the layer thickness of such an artificial soil structure, within a few days or a number of weeks, notch or dryness cracks appear on the soil surface. They are in general only a few millimeters wide but they can also be several centimeters wide.
In normal agriculture and horticulture, such cracks are not advantageous for the plants and cultivation. However, they close again by the swelling which occurs in conjunction with the absorption of water when rain falls or as a result of artificial irrigation or sprinkling. In such cases, such cracks are destroyed or rendered ineffective by following cultivation or other care measures such as hoeing.
However, cracks they have a serious effect on vegetation surfaces which no longer have any connection with supporting soil such as with vegetation mats used to green indoor areas. It is particularly serious if such surfaces are sloping roof surfaces. Thus, due to generally thin layers, dry cracks occur with much smaller intervals than in soil. Due to the limited layer thickness, wind, sun and dryness with their drying, consuming action rapidly reach fine fibrous root systems.
Particularly in the case of extensive greened roof surfaces, the vegetation is of a relatively low and very loose type, which even grows in the gaps. Therefore, the sun, wind, rain, snow and ice have almost unhindered, direct access to such cracks in the substrate, particularly in the substrate surface.
In the case of roof greening, starting from such substrate cracks and in particular at the cut edges, such as directly behind an attic in the case of flat roofs, at corners, and more particularly at ridge and verges, the wind gives rise to extensive erosion effects, which extensively act on vegetation having only a weak root structure.
Such substrates and soils are generally hydrophobic, i.e., if they have dried out, they absorb water only very slowly. This restricts water absorption up to complete swelling, because such cracks are closed again by swelling and last much longer when rain water starts to flow. This leads to very serious water erosion. Frequently roof greening areas of several square meters are eroded as a result of this effect. If in such cases an incorrectly stabilized substrate is used, complete roof surfaces are eroded and slip.
Above and beyond such soil or substrate physical circumstances, particularly in the case of roof greening or when greening surfaces without a soil connection, the problem is to provide such substrates with suitable organic substances. The organic substance normally present in the soil evolves over a period of years or decades through the growth of roots and leaves and the general transformation thereof over a period of years into humus and nutrient humus. Finally such substances are mineralized and are then available to plant roots as absorbable nutrients.
In the case of substrates for surfaces without a soil connection, organic substances only very slowly decay, unlike in the case of plant or root mass. In this way the necessary macropore volume is obtained, so that the plant roots in such greened areas can be supplied with oxygen by means of the corresponding air pore volume. Unlike in agriculture or horticulture, it is not possible in such cases to plough or dig one or more times a year or to hoe for soil ventilation purposes. A too rapid transformation of the organic substance greatly increases the proportion of fines in such substrates, which leads to a rapid loss of the necessary pore volume due to the sealing or clogging of the pores and layers, so that root breathing is limited and is gradually prevented.
The invention seeks to so improve on the aforementioned fiber reinforced pourable vegetation supporting soil substrates, so that it reliably avoids the described disadvantages, i.e. it does not allow dryness cracks as well as wind and/or soil erosion to appear. In addition, the sealing or clogging of the substrate surface due to precipitation or irrigation is to be prevented. It is also naturally advantageous to encourage ecologically advantageous substance cycles. These problems are solved by the vegetation soil substrate and process according to the invention.